What are the Different Types of Alpha Hydroxy Acids?

Alpha hydroxy acids such as glycolic acid, lactic acid, mandelic acid and citric acid are common ingredients in cosmetic and dermatology applications. Other alpha hydroxy acids featured less frequently in dermatological applications are tartaric acid and malic acid. Many skin and anti-aging products utilize alpha hydroxy acids, mainly because of their ability to renew photo-damaged and aged skin.

Glycolic acid is derived from multiple sources, including cantaloupe, pineapple and sugar cane. In skin care products, glycolic acid is used frequently for its ability to penetrate and moisturize the outer layers of the skin because of its small molecular size. Chemical peels and skin products formulated at 10 to 20 percent of glycolic acid are shown to improve skin conditions such as acne, hyperkeratosis, hyperpigmentation and wrinkles.

Derived from sour milk sources, lactic acid is similar to glycolic acid in its effectiveness in treating acne, fine lines, hyperpigmentation and dry skin. Like most of its alpha hydroxy acid counterparts, lactic acid contains skin-hydrating properties that attract and trap moisture within the skin. Typical lactic acid skin care concentrations are 30 to 50 percent, depending on skin type and condition. Unlike other alpha hydroxy acids, lactic acid is naturally produced in very small amounts in humans as a byproduct of anaerobic respiration.

Like lactic acid, citric acid is harvested from food sources such as oranges, lemons and other citric fruits. The alpha hydroxy acid is responsible for providing citric fruits with large amounts of vitamin C, which is an antioxidant. Antioxidants protect the human body from free radical damage and promote healing. Citric acid has many uses, ranging from cleaning products and food additives to cosmetic and pharmaceutical use. Manufacturers of cosmetics, creams and moisturizers use citric acid as a preservative, acid and base balancer.

Similar to other alpha hydroxy acids, mandelic acid has anti-inflammatory and antibacterial properties that benefit people who have rosacea, acne and urinary tract infections. In skin care, mandelic acid is often accompanied by another gentle alpha hydroxy acid called malic acid. Malic acid is mainly extracted from apples and unripe fruits, and it filters toxins and promotes smoother and firmer skin.

Much like malic acid, tartaric acid is responsible for giving foods a sour taste. Tartaric acid, like the aforementioned alpha hydroxy acids, is also used for skin care in the form of creams and lotions. An antioxidant and gentle exfoliant, tartaric acid is mainly found in grapes.